Thermal imaging gear is not going to provide acceptable evidence. Look at the responses to the Gray's Harbor thermal footage or Stacy Brown's thermal footage from Florida. People who believe accept and people who scoff reject. I can't think of anyone who has truly changed their mind about existence based on either.
The value of thermal imagery is indirect: if you get what seem to be "hits" for bigfoot on a thermal imager you know where to deploy other techniques / technologies that might produce results of a more accepted sort.
I can think of several backroad systems I would cruise with a vehicle equipped with high end thermal imagers if I had one available to identify places to set up trail cameras, look for tracks, and knock or call if I were so-inclined. I don't think buying thermal gear is the best choice for an entry level person on a limited budget. Good thermal gear is expensive. the lowest end unit I see much value in is over $7000. (C'mon, lottery ticket!)
At the same time, I'm not sold on GoPro. Unless you're in a real hot spot, activity of ANY sort more than 1 time in 20 is probably delusion. Particularly during daylight hours.
Despite seeming lack of results so far, the best bet we have for photographic evidence is still trail cameras. The best "bait" is yourself. Go camping. Set them up to watch camp. Then forget you ever heard about bigfoot and just have a good camping trip with family. Play games, cook, fish, bring instruments, play some music into the evening around a fire. Be human. Forget stealth, just have fun and be interesting to watch. It will work or it wont, either way, you win.
MIB